libsanitizer/tsan/tsan_update_shadow_word.inc

//===-- tsan_update_shadow_word.inc -----------------------------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file is a part of ThreadSanitizer (TSan), a race detector.
//
// Body of the hottest inner loop.
// If we wrap this body into a function, compilers (both gcc and clang)
// produce sligtly less efficient code.
//===----------------------------------------------------------------------===//
do {
  const unsigned kAccessSize = 1 << kAccessSizeLog;
  u64 *sp = &shadow_mem[idx];
  old = LoadShadow(sp);
  if (LIKELY(old.IsZero())) {
    if (!stored) {
      StoreIfNotYetStored(sp, &store_word);
      stored = true;
    }
    break;
  }
  // is the memory access equal to the previous?
  if (LIKELY(Shadow::Addr0AndSizeAreEqual(cur, old))) {
    // same thread?
    if (LIKELY(Shadow::TidsAreEqual(old, cur))) {
      if (LIKELY(old.IsRWWeakerOrEqual(kAccessIsWrite, kIsAtomic))) {
        StoreIfNotYetStored(sp, &store_word);
        stored = true;
      }
      break;
    }
    if (HappensBefore(old, thr)) {
      if (old.IsRWWeakerOrEqual(kAccessIsWrite, kIsAtomic)) {
        StoreIfNotYetStored(sp, &store_word);
        stored = true;
      }
      break;
    }
    if (LIKELY(old.IsBothReadsOrAtomic(kAccessIsWrite, kIsAtomic)))
      break;
    goto RACE;
  }
  // Do the memory access intersect?
  if (Shadow::TwoRangesIntersect(old, cur, kAccessSize)) {
    if (Shadow::TidsAreEqual(old, cur))
      break;
    if (old.IsBothReadsOrAtomic(kAccessIsWrite, kIsAtomic))
      break;
    if (LIKELY(HappensBefore(old, thr)))
      break;
    goto RACE;
  }
  // The accesses do not intersect.
  break;
} while (0);